Neural Action Codec for Vision-Language-Action Models
NAC, a neural audio codec-inspired architecture, compresses robot action trajectories as multi-channel 1D signals using multi-scale residual vector quantization. By replacing mel-spectrogram losses with time-domain and non-mel spectral reconstruction, NAC achieves high-fidelity action encoding with minimal architectural changes, outperforming existing tokenizers in reconstruction error and success rates on real-world manipulation tasks.